Screen/tray method and system for wet sulphur priller

ABSTRACT

Relatively uniform spherical shaped solid pellets (prills) may be created by passing molten sulfur through a nested strainer to remove particles that would otherwise become trapped in the system, a drip tray with a heating channel attached on its underside, an injection conduit for delivery of a cooled zone of water to create solid prills, and thereafter moving the prills through a stationary curved screen to remove most of the excess water and a vibrating screen.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/644,183 filed on Dec. 22, 2009, now U.S. Pat. No. 8,011,911, which isa continuation of U.S. application Ser. No. 11/977,827 filed on Oct. 26,2007, now U.S. Pat. No. 7,638,076, all of which applications are herebyincorporated by reference for all purposes in their entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

N/A

REFERENCE TO MICROFICHE APPENDIX

N/A

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to the field of converting moltensulfur (or sulphur) into solid pellets (or prills).

2. Description of the Related Art

Sulfur is used in numerous products, including fertilizers, gunpowder,insecticides, fungicides, paper, and textiles. It may be extracteddirectly from the earth, or it may be removed from other naturalsubstances, such as coal, natural gas, or crude oil. Liquid or moltensulfur produced as a by-product from petro-chemical refineries oftencontains particulate impurities known as “Carsul,” which is a carbonsulfur polymer. Sulfur is usually produced, transported, and utilizedwithin the United States in molten liquid form. It is inconvenient andexpensive to store and transport sulfur in a molten form. In addition,before sulfur can be exported, generally, it has to be converted tosolid form.

The prior art contains proposals for converting liquid or molten sulfurinto pellets (known sometimes as “prills”). For example, “Wet” processespropose forming and solidifying droplets of sulfur in a liquid coolant.U.S. Pat. No. 4,149,837 proposes converting molten sulfur into solidpellets by passing droplets through a liquid medium at temperatures inexcess of 150° F., and preferably with the liquid medium approaching themelting point of sulfur.

U.S. Pat. No. 3,649,217 proposes separating sulfur from crushed ore bypassing the crushed ore containing sulfur through a hot water section inthe range of 290°-320° F. that melts the sulfur, and then through a coldwater section in the range of ambient to 150° F. According to the '837patent, the quenched pellets are usually hollow, pocked with pin holes,resemble somewhat pieces of popcorn, crumble when extensively handled,and tend to retain moisture.

U.S. Pat. No. 4,133,669 proposes forming prills from a moltensulfur-bentonite mixture by passing the mixture through a liquid coolingmedium comprising liquid fertilizer. The '669 patent proposes that ifthe liquid cooling medium was water, or contained an excessive amount ofwater, the mixture would not become pelletized, but would degrade andturn into “mush” as the mixture entered the water.

For maximum commercial value, sulfur prills should be generallyspherical in shape, uniform in size and density, and have low moisturecontent. Very small or fine pieces of sulfur, commonly known as “fines,”are undesirable and create an enormous maintenance problem and potentialfire and safety hazards and health problems for manufacturing personnel.High moisture content is undesirable because, among other things, thecustomer typically pays by weight, and less sulfur is received. Further,the increased weight increases the cost of shipping, and water andsulfur may create dangerous sulfuric acid. Sulfur prills typicallyshould have a moisture content of 1.8% to 2.2% to command maximumcommercial value and be acceptable for export. Moreover, the prillstypically should meet the size and uniformity criteria set forth belowin Table 1.

TABLE 1 Shape, size, and size distribution: Generally smooth and free ofangularities 90 percent must remain on #4 Tyler Mesh screen (4.75 mm) to#16 mesh screen (1.18 mm) No material should exceed 6 mm in diameter Nomore than 10 percent retained on the #4 mesh screen No more than 10percent should pass the #16 mesh screen No more than 2 percent passing a50 mesh screen

A need exists for a method and system to convert liquid or molten sulfurto solid prills that produces prills meeting the size, uniformity, andmoisture content criteria generally described above for maximumcommercial value. The method and system would use an economical novelwet process of quenching the sulfur through a liquid medium, such aswater.

BRIEF SUMMARY OF THE INVENTION

A method and system is disclosed for converting liquid sulfur into solidpellets or prills that are generally spherical in shape, without sharpedges, uniform in size and density, and have relatively low moisturecontent. A two-stage nested strainer removes impurities from the moltensulfur that may otherwise contribute to maintenance delays. A heateddrip tray creates uniform droplets of liquid sulfur. A heating systemfor the drip tray is incorporated onto the underside of the tray so asto allow efficient and uniform heating while minimizing any impact onoperations should a leak occur. The droplets are passed through aforming tank that contains a liquid medium, such as water. In theexemplary embodiment, the bottom portion of the forming tank funnels theprills and water through a relatively smaller opening. Relatively warmwater may be injected near the bottom of the tank. A lesser amount ofrelatively cool water is injected through novel injection conduits nearthe top surface of the water. The injection conduits create a cool mediazone in the top area of the forming tank where prills are initiallyformed. Solid prills accumulate in the bottom section of the formingtank. A sensing device detects when a sufficient number of prills havebeen accumulated in the forming tank, and activates a discharge gatevalve to release the prills while maintaining a level of water in theforming tank to adequately continue the process. The prills exit theforming tank and traverse down a static curved screen to a vibratingscreen. A multi-stage filtration system removes the fines and allows thefiltered water to be re-circulated and cooled in a closed system. Theprills are then transported to a medium for storage or transportation.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained with thefollowing detailed descriptions of the various disclosed embodiments inthe drawings, which are given by way of illustration only, and thus arenot limiting the present invention, and wherein:

FIG. 1 is an overall schematic view of a sulfur prilling systemaccording to the invention showing an exemplary layout of a nestedstrainer, a drip tray, an overflow container, a sulfur prill formingtank, a discharge gate valve, a curved screen, a vibrating screen, afiltration system for the cooling medium, a cooling system for thecooling medium, and a conduit system.

FIG. 2 is a side elevational view of a prill tray mounted on an overflowcontainer and positioned over a forming tank, a discharge gate valvepositioned below the bottom of the tank, and a curved and a vibratingscreen disposed together below the discharge gate valve.

FIG. 3 is a front elevational view of a nested strainer positioned overa prill tray mounted over a forming tank, with an overflow container atthe top of the tank.

FIG. 4A is an elevational view of a strainer housing with the internalfilters removed, and conduits attached to the housing.

FIG. 4B is a plan view of the strainer housing and conduits of FIG. 4A.

FIG. 5A is an elevational view of a strainer housing.

FIG. 5B is a plan view of the strainer housing of FIG. 5A.

FIG. 5C is an elevational view of a large basket filter.

FIG. 5D is a plan view of the filter of FIG. 5C.

FIG. 5E is an elevational view of a small basket filter.

FIG. 5F is a plan view of the filter of FIG. 5E.

FIG. 6 is an elevational section view showing one half of a small basketfilter positioned inside one half of a large basket filter, both ofwhich are disposed inside one half of a strainer housing.

FIG. 7A is a plan view of a drip tray with a channel shown in phantomattached underneath.

FIG. 7B is a left side elevational view of the drip tray and channel ofFIG. 7A.

FIG. 7C is a right side elevational view of the drip tray and channel ofFIG. 7A.

FIG. 7D is a front elevational view of the drip tray and channel of FIG.7A.

FIG. 8A is a front elevational view of a forming tank with an overflowcontainer at the top.

FIG. 8B is a plan view of the forming tank and overflow container ofFIG. 8A.

FIG. 9A is a back elevational view of the forming tank and overflowcontainer of FIG. 8A.

FIG. 9B is a section view taken along line 9-9 of FIG. 9A to better showthe opening.

FIG. 10 is a left side elevational view of the forming tank and overflowcontainer of FIG. 8A with a discharge gate valve in phantom attachedbelow the bottom of the tank.

FIG. 11A is a right side elevational view of the forming tank andoverflow container of FIG. 8A with a discharge gate valve in phantompositioned below the bottom of the tank.

FIG. 11B is a plan view of the forming tank and overflow container ofFIG. 11A.

FIG. 12A is an isometric view of the top of a forming tank with twoconduits entering the top of the tank and a conduit ring positionedinside.

FIG. 12B is a section plan view taken through a forming tank of twoinjection conduits each in communication with a conduit extendingoutside of the tank.

FIG. 12C is a cut away section isometric view through a forming tank ofone complete injection conduit and another partial injection conduit,both containing several ports.

FIG. 12D is a section view taken along line 2-2 of FIG. 12C to bettershow a port in an injection conduit.

FIG. 13A is a front elevational view of a discharge gate valve.

FIG. 13B is a side elevational view of the valve of FIG. 13A.

FIG. 13C is an enlarged view of the designated area of FIG. 13B.

FIG. 14 is an elevational view of a curved screen over a basin, bothshown in phantom, which curved screen is positioned with a vibratingscreen, which is shown partially in phantom.

FIG. 15 is an elevational view of a tank with a conical lower section incommunication with four hydro-cyclones in series, and a container.

DETAILED DESCRIPTION OF THE INVENTION

Generally, the present invention involves a method and system forconverting liquid or molten sulfur to solid pellets or prills that aregenerally spherical in shape, are without sharp edges, uniform in sizeand density, and have relatively low moisture content. The method andsystem produce prills that generally meet the narrow size distributionand uniformity criteria set forth in Table 1 above. Although thepreferred use of the method and system is for sulfur, it is alsocontemplated that the method and system, and any of the embodiments andcomponents, may be used for converting other molten liquids to solidprills, such as asphalt. Although the exemplary embodiment of the methodand system passes the molten sulfur through water, other fluids orcooling medium besides water, as known in the art, but novel when usedherein, may be used.

Turning to FIG. 1, block valves 12, an actuated valve 18, a flow meter16, and a pump 14 are positioned along conduit 10. One end of conduit 10is positioned with a nested strainer 20, wherein the strainer 20 ismounted over a drip or prilling tray 30. The liquid or molten sulfur mayenter through the other end of conduit 10 and travel toward the strainer20. The drip tray 30 may be positioned over a forming tank 40. Adischarge or knife gate valve 50 may be mounted below the bottom 77 ofthe forming tank 40 in a discharge channel 96. A static curved screen 60may be positioned below the forming tank 40 and the discharge gate valve50. A vibrating screen 70 may be disposed with the curved screen 60.

A conduit 80 may be attached to a lower section 76 of the forming tank40, and a conduit 90 may be attached below the top of the forming tank40 in an initial prill forming zone. The lower section 76 of the formingtank 40 is constructed so as to funnel the prills (and some of the tankmedia, e.g., water) to the discharge channel 96. As will be discussedbelow in detail, in one embodiment the relatively warm water may enterthe forming tank 40 through the conduit 80, and a lesser amount ofrelatively cool water may enter the forming tank 40 through one or moreconduits 90. More than one of each of the conduits (80, 90) maycommunicate with forming tank 40. In one embodiment, two conduits 90 maycommunicate with the forming tank 40 through novel injection conduits103, which will be described below. When the system is operating, theforming tank 40 is filled with the medium, such as water.

The water may exit the forming tank 40 through conduits (100, 120),which may each be attached on one end with an overflow container 130attached at the top of the forming tank 40. A sensor LIT1 is positionedto maintain an overflow condition into the overflow container 130. Asensor LIT2 is positioned to maintain the desired level of molten sulfurin the drip tray 30. One end of the conduit 120 may be positioned with atank 140. The forming tank 140 may have a funneling shaped bottom orlower section as described herein. One end of each of conduits (142,144) may also be positioned with the tank 140. While the system is innormal operation, the conduit 142 may transport the water removed fromthe curved screen 60, and the conduit 144 may transport the waterremoved from the vibrating screen 70. One end of the conduit 146 may bepositioned with a storage tank 150. The conduit 146 may be used totransport the water removed from the curved screen 60 to the tank 150while the system is not in operation and is being maintenanced. The tank150 may be used for temporary storage.

Hydro-cyclones (160, 170) may be positioned in series along the conduit152. Two or more hydro-cyclones may be positioned in series. In oneembodiment, four hydro-cyclones may be positioned in series. Differentsized hydro-cyclones may used to remove different sized particles fromthe liquid. One end of the conduit 100 may be positioned with a tank180. One end of the conduit 162 may be also positioned with the tank180. The tank 180 may have a conical bottom section. The conduit 162 maytransport filtered water from the hydro-cyclones (160, 170). One end ofthe conduit 164 may be positioned with the tank 180. The conduit 164 maytransport the water from an outside source to introduce new water to theprocess. A conduit 182 may transport the water from the tank 180 to achilling package or cooling system 190. A conduit 184 may transport thewater from the tank 180 to a cooling system 192. The cooling system 190may be a heat exchanger and refrigeration unit, and the cooling system192 may be a cooling tower. As can now be understood, FIG. 1 shows aclosed loop sulfur prilling system in which the water may be filteredand cooled before recirculation back to the forming tank 40. As will bediscussed below, level detection devices may be in the tanks (140, 180)so that a central processing unit (CPU) (not shown) may control acombination of diverting valves and variable speed pumps to maintainappropriate water levels and pressures at all times.

Turning to FIG. 2, a drip tray 30 may be positioned over a top 63 of theforming tank 40 using leveling fasteners such as threaded rods 42attached with the overflow container 130. The drip tray 30 can beremoved and replaced for easy maintenance. The overflow container 130may be attached to the forming tank 40 and extend over its top 63. Oneend of each of conduits (100, 120) may be attached with and extend fromthe overflow container 130. One end of conduit 90 may be attached withthe forming tank 40. In one embodiment, another conduit 90 may beattached with the forming tank 40 on the opposite side that is hiddenfrom view in FIG. 2, such as shown in FIG. 12B.

Returning to FIG. 2, a discharge gate valve 50 may be positioned belowthe lower section 76 of forming tank 40 in a discharge channel 96. Aswill be discussed below, in one embodiment, a valve 50 may be placed atan angle from the horizontal as shown in FIG. 2 using flanges 68 in thedischarge channel 96. A static curved screen 60 may be disposed belowthe discharge gate valve 50, and the vibrating screen 70 may bepositioned with and at least partially below the curved screen 60. Abasin 65 may be positioned below the curved screen 60 to capture waterthat may be separated from the prills as they travel down the curvedscreen 60.

In FIG. 3, a conduit 10 passes through an actuated valve 18. One end ofthe conduit 10 may be positioned with the nested container 20. Liquid ormolten sulfur may enter the top of a strainer housing 21 and exitthrough a conduit 23, with a conduit 22 being used for overflow. Thedrip tray 30 may be mounted with leveling fasteners such as threadedrods 42 over the forming tank 40. The overflow container 130 may beattached to the forming tank 40 and extend above its top 63. A sightwindow 67 may be in the lower section 76 above bottom 77 of the formingtank 40. Flanges 68 allow a discharge channel 96 from the forming tank40 to be curved until an opening 78. The basin 65 may be positioned tocapture water from the curved screen 60.

FIGS. 4A and 4B show an exemplary strainer housing 21 and conduits (22,23) of the novel nested strainer 20. A notch 25 in the strainer housing21 may be used for positioning an arm 27 of a large basket filter 28, aswill be described below in conjunction with FIGS. 5C and 5D. Althoughonly one notch 25 is shown in FIG. 4A, there may be more than one notch25 to mate with more than one arm 27. In one embodiment, there may bethree notches 25 positioned an equal distance around the circumferenceof the strainer housing 21 as it is viewed in FIG. 4B. The notch 25 maybe 13/16 inches (2.06 cm) wide and 2⅜ inches (6.03 cm) long. It is notedthat the sizes and dimensions provided herein are for a smaller prillingsystem. Other systems may utilize different sizes and dimensions for thevarious components without departing from the spirit of the presentinvention. The strained or filtered molten sulfur will exit at a nozzle26. The housing and nested filters are heated and remain heated duringoperation. The housing and nested filters are heated by steam, althoughother methods may be used. The conduit 22 is generally for overflow. Theconduit 23 may be 1½ inch (3.81 cm) diameter pipe, and the conduit 22may be 1 inch (2.54 cm) diameter pipe. The strainer housing 21 may be acylindrical shape with a 10 inch (25.4 cm) diameter and a 12 inch (30.5cm) height.

All components of the nested strainer 20 are generally stainless steel,although other corrosive-resistant and compatible materials, known inthe art, but novel when used herein, may be used. A sensor 24 may bepositioned along the interior of the conduit 22, near the midpoint ofits length. The sensor 24 detects flow, although other characteristicssuch as temperature, pressure, and/or other information may be detected.The sensor 24 may be mechanical, electrical, hydraulic, pneumatic, orsome other means as is known in the art, but novel when used inconnection with the invention. Information from the sensor 24 may bereceived by a CPU (not shown), and that an actuated valve 18 may becontrolled remotely by such CPU. The actuated valve 18 may bemechanical, electrical, hydraulic, pneumatic, or some other means as isknown in the art, but novel when used in connection with the invention.The conduit 10 may be closed at the valve 18 should flow be detected bythe sensor 24 or diverted to alternate strainer/filter(s).

Turning to FIG. 5A, ports (33, 34) in the housing 21 provide a pathbetween the interior of the housing 21 with the conduits (23, 22). Theport 33 may be 1½ inch (3.81 cm) diameter to match the conduit 23, andthe port 34 may be 1 inch (2.54 cm) diameter to match the conduit 22.The center of the port 33 may be positioned 1 inch (2.54 cm) above thebottom of the housing 21, and the center of the port 34 may bepositioned 9 inches (22.86 cm) above the bottom of housing 21.

Turning to FIGS. 5C and 5D, a large basket or internal filter 28comprises a top ring 31, arms 27, and a mesh basket 29. The mesh 29 maybe attached to a top ring 31. The mesh 29 and the top ring 31 aregenerally a combined height of 10 inches (25.4 cm). They have a diameterof 8 inches (20.32 cm). The top ring 31 is generally 2¾ inches (7 cm) inheight. The mesh 29 generally contains smaller openings than mesh 35,which is shown in FIG. 5E. Openings in the mesh 29 may be smaller thanthe diameter of holes 53 in the drip tray 30, as will be described inconjunction with FIG. 7D. The nested strainer 20 may trap Carsul,particles, and other impurities that would be large enough to partiallyor completely plug holes 53 in the drip tray 30. Returning to FIG. 5C,the arms 27 are attached to the top ring 31 generally 2 inches (5.08 cm)below the top of ring 31. The arm 27 is generally cylindrical in shape,with a length of 2½ inches (6.35 cm) extending from the exterior surfaceof the top ring 31, and a washer positioned 1¾ inches (4.45 cm) from thefree end of the arm 27. The arms 27 may be positioned at an equaldistance away from each other along the circumference of the top ring 31as viewed in FIG. 5D.

The notch 32 in the top ring is generally 13/16 inches (2.06 cm) wideand 1⅛ inches (2.86 cm) long. There may be three notches 32 in the topring 31 spaced at an equal distance away from each other along thecircumference of the top ring 31 as viewed in FIG. 5D. The fullyassembled nested strainer 20, such as partially shown in FIG. 6, thearms 27 may rest in the notches 25, and arms 37, which are shown inFIGS. 5E and 5F, may rest in the notches 32.

Turning to FIGS. 5E and 5F, a small basket or internal filter 39comprises a top ring 42, arms 37, and a mesh basket 35. The mesh basket35 may be attached to the top ring 42. The mesh basket 35 and the topring 42 are generally a combined height of 8½ inches (21.6 cm). Theygenerally have a diameter of 6 inches (15.24 cm). The top ring 42 isgenerally 1½ inches (3.81 cm) in height. The mesh basket 35 containslarger openings than the mesh basket 29, which is shown in FIG. 5C. Ascan now be understood, when the small filter 39 is positioned in thelarge filter 28, the mesh basket 35 will trap larger particles, and meshbasket 29 will then trap smaller particles that escape with the moltensulfur through the mesh basket 35. Returning to FIG. 5E, arms 37 areattached to the top ring 42 generally ¾ inches (1.91 cm) below the topof ring 42. The arm 37 is generally cylindrical in shape, with a lengthof 1½ inches (3.81 cm) extending from the exterior surface of the topring 42, and a washer positioned ¾ inches (1.91 cm) from the free end ofthe arm 37. The arms 37 may be positioned at an equal distance away fromeach other along the circumference of the top ring 42 as viewed in FIG.5F.

As shown in FIG. 6, the small basket filter 39 may be positioned in thelarge basket filter 28, which may both be positioned in the strainerhousing 21. The liquid or molten liquid sulfur that contains impuritiesand particles, such as Carsul, may enter the top of the nested strainer20. When the filters (28, 39) become clogged with such impurities, thenthe liquid or molten sulfur will begin to flow out the port 34 andthrough the conduit 22 and be detected by the sensor 24, which maysignal the CPU to shut off the flow, or divert the flow to anotherstrainer/filter(s). The filters (28, 39) may be easily removed andcleaned. Multiple identical filters (28, 39) may be available so thatwhen one set may become clogged, replacements may be used to continueoperations while the others are being cleaned. There may be more or lessthan two filters (28, 39) in the strainer 20. A system of more than onenested strainers 20 may be placed in series or parallel, each nestedstrainer 20 containing more or less than two internal filters (28, 39).The primary advantage of the nested strainer 20 is in its removal ofimpurities such as Carsul from the liquid sulfur before it plugs orobstructs holes 53 in the drip tray 30, as will be discussed below inconjunction with FIG. 7A. The filters (28, 39) are much easier to clean,and not nearly as expensive to replace, as drip tray 30. When the nestedstrainers 20 are placed in parallel, system operation may continue whenreplacing one set of nested strainers 20.

Turning to FIGS. 7A through 7D, a channel 52 may be attached to theunderside 101 of the drip tray 30. The channel 52 may be a half pipewelded to the underside 101 of the tray 30. However, other types andsizes of the channel 52, as well as attachment means as known in theart, but novel when used in the present invention, can be used. Aconduit 51 may connect with the channel 52. When the liquid or moltensulfur is poured into the drip tray 30, it must be kept sufficiently hotto maintain the proper viscosity so as to allow the sulfur toeffectively flow though the drip tray 30 during the normal operationprocess. Steam may run through the conduit 51 and the channel 52 touniformly heat the drip tray 30 through thermal conduction or other heattransfer mechanisms. In addition, other fluids or gases as known in theart, but novel when used herein, may be used to heat the drip tray 30.Although one channel 52 in the system is shown, there may be more thanone channel 52, and that the separate channels may not be coupled witheach other. The conduit 52 may be 1 inch (2.54 cm) diameter Schedule 40stainless steel pipe, and that the channel 52 may be such same pipe cutin half along its length. The snake like pattern of channel 52 insuresthat tray 30 will be heated uniformly and remained heated duringoperation. However, other patterns can be used so that the drip tray 30remains heated.

In one embodiment, the drip tray 30 may be approximately square in planview as seen in FIG. 7A. In one embodiment, its width would be 2′-2¼″(66.68 cm) and its length 2′-1¼″ (64.14 cm). In one embodiment,longitudinal centerline 54 of the conduit 51 is 3⅞ inches (9.84 cm) fromthe side of the drip tray 30 as viewed in plan in FIG. 7A. Thelongitudinal centerlines 54 of straight sections of the channel 52 underthe drip tray 30 as shown in FIG. 7A are generally spaced 6¼ inches(15.88 cm) apart. The depth or height of tray 30 may be 6 inches (15.24cm). The location of the channel 52 underneath the drip tray 30 has theadvantage of allowing the steam or other gas or fluid to be in directcontact with the underside of the drip tray 30, which makes the heatingmore efficient. This arrangement allows the entire drip tray 30 to heatup and expand homogeneously, eliminating separation and expansioncracks. Further, in the event there is a leak that develops in thechannel 52 or its welds, steam condensate would simply drip into theforming tank 40 below, and allow operations to continue until the nextscheduled shut down.

In one embodiment the drip tray 30 contains 521 uniform sized holes 53through which liquid or molten sulfur may pass and form into droplets.However, a single drip tray 30 may contain 5000 or more holes 53. Theremay be more than one drip tray 30 used at a time, so as to provide 5000or more holes 53. The holes 53 are circular and generally 3/32 inch(0.24 cm) in diameter. The holes 53 are generally located on a onesquare inch (2.54 cm) grid. The holes 53 are generally no closer than 1½inches (3.81 cm) from the longitudinal centerline 54 of the channel 52,which insures that droplets remain a sufficient distance from thechannel 52.

Without the advantage provided by the nested strainer 20 of the removalof impurities from the liquid or molten sulfur, the holes 53 willgenerally become plugged or obstructed, which will necessitate anunscheduled shut down of operations. Whereas it is a labor intensive andtime consuming process to remove one or more drip trays 30 and scrapeout and clean hundreds or thousands of holes 53, it is much moreefficient to change the filters (29, 35) of the nested strainer 20. Thedrip tray 30 may need to be cleaned two times a day while in operationif operated without the strainer 20. Moreover, when cleaning out orunclogging the relatively small and fragile holes 53 in the drip tray30, it is likely that many of the holes 53 will become worn,particularly with multiple cleanings over time. This will lead to theholes 53 becoming enlarged and non-uniform in size, which will affectthe geometry of the resultant prills and cause them to be non-uniform insize. Replacement costs for the drip tray 30 are much higher than forthe filters (29, 35). The drip tray 30 may generally be made ofstainless steel. However, other non-corrosive materials, as known in theart, but novel when used in the present invention, may be used. Angles55 or other attachment members may be attached along the length of thedrip tray 30 for use in attachment with forming tank 40.

Turning to FIG. 8A, the overflow container 130 may be attached near thetop 63 of the forming tank 40. The top 75 of the overflow container 130is above the top 63 of the forming tank 40. Four threaded rods 42 areattached to the top 75 of the overflow container 75. The drip tray 30may be attached with threaded rods 42 using nuts or other levelfastening means. The underside 101 of the drip tray 30 may generally beplaced approximately 2 inches (5.08 cm) above the water surface in theforming tank 40. Tests have indicated that when the distance isapproximately 2 inches, the produced prills generally meet thecharacteristics identified in Table 1 with a moisture content in therange of 1.8 percent to 2.2 percent. The water surface will be at top 63of the forming tank 40. The threaded rods may be one inch (2.54 cm)diameter and 1′-1½″ (34.3 cm) long. Since the top 63 of the forming tank40 is below top 75 of an overflow container 130, when water reaches thetop 63 it will spill into the overflow container 130.

Couplings 61 are attached to the forming tank 40 and said couplings 61allow communication with the interior of the forming tank 40. Thecouplings 61 may be 3 inch (7.62 cm) diameter. In one embodiment, twoconduits are used, such as the conduit 90 shown in FIGS. 1 and 2, andconduits 90 shown in FIG. 12B, may be attached with couplings 61 totransport cool water into the forming tank 40 through a conduit ring 94or injection conduits 103, as will be discussed in conjunction withFIGS. 12A through 12D below. Couplings 62 may be attached to an overflowcontainer 130 and allow communication with the interior of container130. As shown in FIG. 8B, there may be two couplings 62. The twoconduits (100, 120), as shown in FIGS. 1 and 2, may be attached with thecouplings 62 to transport water that has spilled into the overflowcontainer 130. The coupling 71 may be used for sensors or othermeasurement devices to measure temperature, flow, pressure, and/or otherinformation.

The coupling 64 may be attached to the lower section 76 of the formingtank 40 and allow communication with the interior of the forming tank40. The conduit 80 as shown in FIG. 1 may be attached with the coupling64 to transport warm water to the forming tank 40, as will be discussedin detail below. The couplings (66, 69) may be used for overflow. Thesight glass 67 may be positioned in the lower section 76. The height ofthe combined forming tank 40 and the overflow container 130 from the top75 of container 130 to the bottom 77 of the tank 40 may generally be12′-9 7/16″ (3.9 m). The height of overflow container 130 may be 2′-1¼″(64.14 cm). Attachment members (72, 73) may be used to support theforming tank 40 on a frame as shown in FIG. 2.

Returning to FIG. 8A, flanges 68 may be used to change the direction ofdischarge the channel 96 after exiting the bottom 77 of the forming tank40. The outlet 78 may generally be rectangular in shape. The opening inbottom 77 of the forming tank 40 may be rectangular in shape and similarin size to the outlet 78. The advantages of a generally funnel-shapedlower section 76 include that its shape minimizes the crushing effectthat gravity and rubbing action may have on the prills, and also that itdirects the prills toward the bottom 77. The advantages of transitioningto a rectangular opening in the bottom 77 of the forming tank 40 includethat it eliminates a choke point or bottle neck for the prills thatwould otherwise occur with a circular opening, which would likely causeplugging of the circular opening with prills. It is generally costly andtime consuming to unplug such an opening. Significantly, the rectangularshape allows the prills to be distributed uniformly later on the curvedscreen 60, as will be discussed below in detail.

The sensing device 74 may be positioned on the exterior of the formingtank 40 around the middle of the height of the lower section 76. In oneembodiment, the sensing device 74 is a nuclear sensing device that maygenerate a wide beam from a radioactive material contained in atransmitter that may be radiated across the forming tank 40, and thechange in intensity detected at the opposite side of the forming tank 40by a tubular receiver (not shown). Because the beam will penetrate in adifferent way through the water than through the area where prillaccumulation exists, the exact level of prills may be detected by thereceiver. The information from the sensing device 74 may be transmittedto the CPU (not shown), which may signal the actuator 91 of thedischarge gate 50 in order to control constant level of prills in thelower section 76 of the forming tank 40. Other sensing devices may beused as well. Such other sensing devices may be electrical, mechanical,hydraulic, pneumatic, or some other means.

FIG. 9A is similar to FIG. 8A, but is viewed from a different direction.Turning to FIG. 9B, the outlet 78 is generally 5 inches (12.7 cm) by 20inches (50.8 cm). The flange 68 may be 10 inches (25.4 cm) by 2′-0″ (61cm).

Turning to FIG. 10, the discharge gate valve 50 may be positioned belowthe bottom 77 of the forming tank 40 and above the outlet 78 along thedischarge channel 96. As previously described, the discharge gate valve50 may be remotely operated based upon information the processorreceives from the sensor 74. The longitudinal axis 83 of the dischargegate valve 50 may generally be at a 60° angle from the horizontal axisto allow easy discharge of the prills. The discharge gate valve 50 isdiscussed below in conjunction with FIGS. 13A-13C.

Returning to FIG. 10, the distance between outside surface 81 of theoverflow container 130 and an outside surface 79 of the forming tank 40allows water that flows over the top 63 of the forming tank 40 to becaptured in container 130. The trapped water may flow out of thecouplings 62, which create ports in the container 130. FIG. 11A showsthe forming tank 40 from a different direction. An access opening 82 maybe covered with a metal plate when the access opening is not in use.

Turning to FIG. 12A, in one embodiment the conduit 93 may be incommunication with two conduits 95 (only one is shown) that may extendapproximately 12 inches (30.5 cm) below the surface of the water into atank 97. The conduits 95 may be connected with and in communication witha conduit ring 94. The conduit ring 94 may have ports or holes spacedalong the inside of the ring 94 through which water may escape into thetank 97. The ring 94 may be made with approximately 1½ inch (3.81 cm)diameter conduit. The ports may generally be spaced 2 inches (5.08 cm)on center. The port size may be circular with diameter approximately ⅛inch (0.32 cm). The ports may be angled downward at generally 30° fromthe horizontal centerline of ring 94. The conduit ring 94 may havedifferent shapes or sizes. The conduit ring 94 may have ports locatedall around its body. As can now be understood, FIG. 12A shows oneembodiment of how cold water may be delivered to the top of the formingtank 40 through the conduit 93 and out the conduit ring 94. The conduitring 94 may be stainless steel. However, other corrosion-resistant andcompatible materials, as known in the art such as CPVC, but novel whenused herein, can be used. Rather than using the conduits 95 to enter thetank 97 through its top, that the conduits such as the conduit 90 inFIGS. 1 and 2 may transport water to the forming tank 40 through thecouplings 61 shown in FIG. 8A. Once inside the forming tank 40, aconduit ring such as ring 94 in FIG. 12A may be used to disperse waterinto the forming tank 40.

Turning to FIGS. 12B through 12D, an injection embodiment for thedelivery of cool water to forming tank 40 is shown. Each of two conduits90 may be in communication with a different injection conduit 103 asshown in FIG. 12B. Each of the conduits 90 may attach with the injectionconduit 103 at a coupling 61. As previously described, the couplings 61may generally be located approximately 12 inches (30.5 cm) below top 63of forming tank 40. The injection conduit 103 may be made withapproximately 1½ inch (3.81 cm) diameter conduit. As shown in FIG. 12C,the injection conduit 103 may have ports, orifices or holes spaced alongthe inside of the injection conduit 103 through which water may escapetoward the interior of the forming tank 40. The ports 107 may generallybe spaced 2 inches (5.08 cm) on center. The port 107 size may becircular with diameter approximately ⅛ inch (0.32 cm). As shown in FIG.12D, a centerline 105 of the ports 107 may be located at angle θ from ahorizontal centerline 109 of the injection conduit 103. The angle θ maygenerally be 30°. The injection conduit 103 may have different shapes orsizes, such as being “U” or “Y” shaped as seen in plan view. Theinjection conduit 103 may have ports 107 located all around its body.There may be one or more injection conduits 103. The injection conduit103 may be stainless steel. However, other non-corrosive materials asknown in the art, but novel when used in the present invention, may beused. The injection conduits 103 may transport water to the forming tank40. As can now be understood, the embodiments described above inconjunction with FIGS. 12A to 12D show how a relatively cold zone ofwater may be established in an area of the forming tank 40 where prillsare initially formed.

Turning to FIGS. 13A, 13B and 13C, a pneumatic actuator 91 of thedischarge gate valve 50 activates the valve 50 to open and/or close thedischarge channel 96 to the outlet 78 based upon the information theactuator 91 receives from the CPU, which is in communication with thesensor 74. The rectangular opening 78 may act as a spreader bar thatwill allow the prills to slide onto the static curved screen 60 in auniform manner.

As shown in FIG. 14, the curved screen 60 is stationary and maygenerally be positioned below the outlet 78. A basin 65 may bepositioned below the screen 60. The prills will be generally uniformlydistributed along the screen 60 due to the rectangular size of theoutlet 78. The prills may slide down the screen 60 after exiting theoutlet 78. The sliding action will remove water exiting with the prills.Most of the water will be removed from the prills by the curved screen60. This sliding action will gently guide the prills onto the vibratingscreen 70. Most of the water will be removed by the screen 60, and thata vibrating screen 70 may be relatively short, thereby minimizingunwanted mechanical abrasion of the prills which may occur withmechanical vibration. The vibrating screen 70 also allows transportationof the prills to a storage or transportation area. The wedge wire of thescreen 70 may be positioned parallel to the direction of flow of theprills, as shown by arrow on FIG. 14, so as to reduce the filing actionon the prills. The slotted free opening on the vibrating screen 70 maybe 0.02 inches (0.05 cm), which should reduce the amount of fines goingthrough screen 70.

Turning to FIG. 15, the tank 140, also shown in FIG. 1, may be incommunication through a conduit 152 with four hydro-cyclones (160, 161,162, 170), that are aligned in series. One embodiment may contain fourhydro-cyclones (160, 161, 162, 170) in series. The exemplary embodimentmay allow for bypassing one or more of the hydro-cyclones. There may beone or more hydro-cyclones. The tank 140 has a conical lower sectionthat has the advantage of preventing fines from settling out of thewater. Flat bottom tanks quickly fill up with fines, which would requiresuch a system to be taken out of service for an extended period of timeat substantial expense. Impurities such as fines may be removed by thehydro-cyclones (160, 161, 162, 170) and transported to a hopper or tank171. Cleaned water may be discharged into and accumulated in the tank180 as shown in FIG. 1. The cleaned water may leave the tank 180 throughconduits (182, 184). The tank 180 also has a conical lower section.

The filtration system shown in FIG. 15 may be a multiple stage designwhere the water initially goes through one or more hydro-cyclonesdepending on the volume of water to remove sulfur fines up to a certainmicron size. The overflow from the larger hydro-cyclone may subsequentlybe cycled through a series of smaller diameter hydro-cyclones to takeout the ultra fine material before the filtered water is pumped to thecooling tower 192 through the conduit 184 and re-injected through theconduit 80 in the forming tank 40. A smaller portion of the filteredwater may be diverted through the conduit 182 to a chiller package 190where it is cooled to the required temperature and re-injected throughthe conduit 90 near the top of the forming tank 40. As can now beappreciated, the recirculation system is a closed system.

Method of Use

Liquid or molten sulfur may be converted to solid uniform sized prillsusing the process shown in FIG. 1. While the discharge gate 50 may beclosed, relatively warm water in the range of 95° F. to 105° F. may beinjected through the conduit 80 into the forming tank 40. Relativelycold water no warmer than 80% for sulfur prill production, and generallyin the range of 55° F. to 60° F. may be injected through two conduitssuch as the conduit 90 into the upper portion of the forming tank 40approximately 12 inches (30.5 cm) below the top 63. Injection conduits103 as shown in FIG. 12B may be used to deliver the cold water into theinterior of the forming tank 40. The forming tank 40 may be completelyfilled with water. More water may enter through the conduit 80 thanthrough the conduit 90, which may cause an upward draft of water fromthe bottom to the top of the forming tank 40. An average temperature inthe range of 75° F. to 80° F. may be established and maintained in theprill forming zone located approximately 12 inches (30.5 cm) below thetop 63. This method has the advantage of cooling the upper zone of waterwhere the prills are first formed, without the excessive expense ofcooling all of the water in the forming tank 40 to the desiredtemperature range. Overflow water may be trapped by an overflowcontainer 130 and transported away by conduits (100, 120).

Liquid or molten sulfur may enter the system through the conduit 10. Itis transported to the top of the nested strainer 20, through which ittravels through filters (29, 35) and generally out the conduit 23 asshown on FIG. 4A. The nested strainer 20 is heated and remains heatedduring operation to allow the flow of the molten sulfur. If the liquidor molten sulfur travels through the conduit 22, then the sensor 24 maydetect the flow and notify the CPU processor, which may terminate theflow of sulfur through the actuated valve 18 or divert to anotherstrainer/filter(s). In such circumstance, the filters (29, 35) may bereplaced and/or cleaned. The liquid or molten sulfur exits the strainer20 at the nozzle 26 and then enters the drip tray 30, which may beheated by steam flowing through the conduit 51 and the channel 52, asshown in FIG. 7A. Droplets are formed through the gravity flow of liquidor molten sulfur through the holes 53. The drip tray 30 may bepositioned so that the droplets fall approximately 2 inches (5.08 cm) tothe top surface of the water at the top 63 of the forming tank 40.However, other distances may be used to change the size of the prills.

When the droplets enter the prill forming zone of the water near theinjection conduits 103, the liquid or molten sulfur stream breaks downand forms spherical prills by quenching the sulfur in relatively colderwater. The lower water temperature solidifies the outer surface of thesulfur particle, while the sulfur core is still in a semi-plastic state.Interfacial forces are created at the interface between the solid andliquid phase, which pulls the particle into a spherical shape andprevents it from solidifying into an irregular shape. The quicksolidification of the surface typically prevents the prills fromsticking together as they descend to the bottom of the forming tank 40.Once the prills are formed in the forming zone, they travel down bygravity and continue to exchange heat with the upcoming hotter water.This assures further solidifying and cooling of the prill core, but in agentle way. The solidified prills spill out of the bottom of the formingtank 40 at a temperature of generally 105° F. to 115° F. but othertemperature ranges are contemplated.

Generally, while the first prills are being formed, the discharge gate50 may be closed. When a sufficient number of prills fill the lowersection 76 of the forming tank 40, such as for example approximatelyone-half, the sensor 74 may send a signal to the CPU, which maypartially opens the discharge gate 50 so that prills may flow throughthe opening 78 to the curved screen 60. Also, the LIT1 sensor providesthe CPU with information pertaining to the height of the water level inthe forming tank 40. In one embodiment, the distance between the lowerportion of the drip tray 30 and the water in the forming tank 40 isapproximately 2″ (5.08 cm). The discharge gate 50 also opens and closesto maintain a certain level of the sulfur prills in the forming tank 40.The discharge gate 50 includes an actuator (not shown) coupled to theCPU for opening and closing the gate when instructed by the CPU. Thus,the discharge gate 50 may open/close to maintain the amount of sulfurprills in the lower section 76 of the forming tank 40.

As the discharge gate 50 opens and closes to maintain the desired sulfurprill level in the lower section 76 of the forming tank 40, more or lesssulfur prills and water (discharge water) will exit the lower section 76of the forming tank 40. This loss of water will drop the water level inthe forming tank 40 and increase the distance between the drip tray 30and the overflow water level in the forming tank 40. The sensor LIT1will communicate with the CPU to accelerate a variable speed pump toinject additional water through the conduit 80 to compensate for theloss water and maintain the desired distance between the drip tray 30and the water level in the forming tank 40.

The prills will be uniformly disbursed on the curved screen 60 due tothe rectangular opening 78 at the end of the discharge channel 96. Thegate 50 may only partially open so as to allow the warmer water injectedat the bottom of the forming tank 40 to continue to circulate toward thetop of the forming tank 40 which aids in the formation of the sulfurprills. As the prills slide down the curved screen 60, the slidingaction will remove the majority of the water from the prills, which willbe captured in the basin 65. The prills will exit the curved screen 60and enter the vibrating screen 70, where they will have excess finesremoved and dewater by means of mechanical agitation and evaporation toan acceptable moisture range.

As shown in FIG. 1, the water captured from the overflow container 130and the screens (60, 70) may be transported through the hydro-cyclones(160, 161, 162, 170) for removal of the fines. A smaller amount of thecleaned water may be cooled in a chiller package or refrigeration system190, and a larger amount of the cleaned water may be cooled in a coolingtower 192. The water may be re-circulated back to the forming tank 40 ina closed system, with the warmer water entering through the conduit 80,and the cooler water entering through two conduits such as the conduit90. As can now be appreciated, the tanks (140, 180) are not connected,so there is no possibility of cross contamination. Level detectiondevices in the tanks (140, 180) signal information on the levels to theCPU, which controls a series of diverting valves and variable speedpumps to maintain appropriate levels in all tanks at all times. Thepumps feeding the filtration system have fixed flow rates, which supplythe devices with a constant pressure for maximum separation. The size ofthe prills may be changed by adjusting the height of the drip tray 30from the top 63 of the forming tank 40. The size of the prills may bechanged by using different water temperatures in the forming tank 40.The size of the prills may also be changed by using different hole 53sizes or shapes in the drip tray 30.

Sulfur prills produced from this method generally have thecharacteristics identified in Table 1 and minimum moisture content. Theprills are generally spherical in shape, with minimal sharp edges, andhave a very narrow size distribution. Another advantage of the system isscalability of sulfur prill output. The size of the forming tank and thedrip tray generally determine the production rate of the sulfur prills.Thus a smaller forming tank and a drip tray may be used for smallerproduction prill rates and vice versa for larger production prill rates.

The foregoing disclosure and description of the invention areillustrative and explanatory thereof, and various changes in the detailsof the illustrated apparatus and system, and the construction and themethod of operation may be made without departing from the spirit of theinvention.

1. A prilling drip tray, comprising: a tray, said tray comprising topand bottom sides and a port configured to form a droplet, and a channelattached to said tray bottom side, wherein said channel is configured toprovide direct contact of a fluid in said channel with said tray bottomside.
 2. The prilling drip tray of claim 1, wherein said channel is ahalf pipe.
 3. The prilling drip tray of claim 2, wherein said half pipeis welded to said tray bottom side.
 4. The prilling drip tray of claim1, wherein said channel is non-linear.
 5. The prilling drip tray ofclaim 1, wherein said channel is linear in part and non-linear in part.6. The prilling drip tray of claim 1, wherein said channel is configuredto make said fluid change direction as it moves through said channel. 7.The prilling drip tray of claim 6, wherein said channel is configured tomake said fluid change direction by 180 degrees.
 8. The prilling driptray of claim 1, wherein said channel makes more than one pass on saidtray bottom side.
 9. The prilling drip tray of claim 1, wherein saiddroplet is sulfur.
 10. The prilling drip tray of claim 1, wherein saidfluid is steam.
 11. The prilling drip tray of claim 1, wherein saidfluid heats said tray through thermal conduction.
 12. The prilling driptray of claim 1, wherein said tray comprises a plurality of ports forforming a plurality of droplets.
 13. A prilling drip tray, comprising: atray having a top side, a bottom side, and a port configured to form adroplet, and a channel attached to said tray bottom side that isconfigured to make a fluid moving through said channel change direction.14. The prilling drip tray of claim 13, wherein said channel isconfigured to provide direct contact of said fluid with said tray bottomside.
 15. The prilling drip tray of claim 14, wherein said channel is ahalf pipe.
 16. The prilling drip tray of claim 13, wherein said channelis linear in part and non-linear in part.
 17. The prilling drip tray ofclaim 13, wherein said droplet is sulfur.
 18. The prilling drip tray ofclaim 13, wherein said fluid is steam.
 19. A prilling drip tray,comprising: a tray comprising top and bottom sides and a port configuredto form a droplet, and a channel attached to the bottom side of saidtray, wherein said channel is non-linear in part, and wherein saidchannel is configured to allow direct contact of a fluid in said channelwith said tray bottom side.
 20. The prilling drip tray of claim 19,wherein said channel changes direction by 180 degrees.
 21. A strainerfor liquid sulfur, comprising: a strainer housing having a cylindricalshape oriented vertically, a first filter having a cylindrical shapeoriented vertically, and a second filter having a cylindrical shapeoriented vertically, wherein said first filter is disposed in saidsecond filter, and wherein said second filter is disposed in saidhousing.
 22. The strainer of claim 21, wherein said first filtercomprises mesh with a first filter ring around its top edge, whereinsaid second filter comprises mesh with a second filter ring around itstop edge having a notch, and wherein both of said rings have an arm. 23.The strainer of claim 22, wherein said housing has a notch on its topedge, wherein said second filter arm is disposed in said housing notch,and wherein said first filter arm is disposed in said second filter ringnotch.
 24. The strainer of claim 23, wherein said housing has a firstport above a second port, wherein a first conduit is in fluidcommunication with said first port, wherein a second conduit is in fluidcommunication with said second port, and wherein said first conduitintersects with said second conduit.
 25. The strainer of claim 24,further comprising a sensor in said first conduit configured to detectfluid flow and send a signal to a processor in response to said flow.26. The strainer of claim 24, wherein said housing is configured toreceive the unstrained liquid sulfur through its top, and to movestrained liquid sulfur through said second port.